Method of forming a sacrificial lubricating layer



United States Patent (Mi METHOD, on FORMING A"SACRIFICIAL' LUBRICATING LAYER anie J-f l me, Arlington, town, N. J., assignors to Verona, NJ.

No Drawing. Applicafion January-18,1954

. SeriaLNo. 404,796

4 claims. (Cl. 204-181 andFreden'c'k Fahnoe, Morris! Vitro Corporatio' rof America,

method of: producing lubricharacterized by variable thickness, poor adherence to the .metal, and, in certain situations, inadequatelubricating and anti-seizing properties;

Accordingly, it is. an object of.- the present invention both to provide a metal, structure. having a lubricant coating which obviates the. above disadvantages and a novel method for applyingthis coating.

Another object is to provide .a'metal structureyhaving a. lubricant coating which 3 will adhere well. to. the, struca ture until. the desired metal. working operation. is per-'- formed and which canabe readilystripped from the. struc; ture during this operation. 4 Still, another object isrto provide a method for.electr-. phoretically depositing asolid lubricantcoating on ametalstructure.

Yet another-object is to provide a metal structure having a lubricant coa-ting, with excellent lubricating'and.

' antiaseizingproperties.

Still a further object isIto provide-a lubricant coating which will reduce the coeifieient; of friction of metalspossessing adhesive properties as,well asthose metals. which cannot be surface hardened;

a Our invention; contemplateswthe 'electrophoretic codeposition of reducible or "decomposable. metallic com: pounds .andlaminated metallic lubricating. agents 'on'ia metal. structure of sequent reduction or decomposition of metal of the deposited reducible compoundto form a metal, matrix whichds; bonded-to thestructure and which in turn en-- traps andrbonds the lubricating agent or agents to the the character indicatedand the sub 2,830,017 Patented. Apr. .8, 1958 tallic atoms to. form layers on: both :sides of thisplane. The non-metallic atoms in each 'ofrthe. several crystals thus formed have very little attraction for-'eachi'other, sopthat these crystals willrslipi readily with. respect to each: other: under the action of low shearing: forces. Moreover, the non-metallic atoms have an affinity for ice A adjacent metal surfaces, sothat the-crystals attachedto 7 The term laminated phoretically forming a. friction element structure. to form a lubricant coating. The amountsof lubricant and matrix forming material are such. that the layer after reduction. contains70.80;% byweight of me- The rela-' tallie. matrix. and 3 07-20% of solid lubricant.

tive P oportions of the reducible compounds and lubi-.

cating agents. are such, thatthe lubricant. coating will adhere uniformly "to the structure until: the structure is subjected to a metal working operation such as deep drawing. Duringthis operation; the, coating, while supplying the desired; amount of lubrication, is progressively worn awayor stripped from the structure. The term has been-seleeted todenote this type of coating and this termwill be used hereinafter.

' Certaininorganic compounds of metals and non-metals, for example, the "sulphides, disulphides, selenides, and

tellurides of suchmetals as molybdenum, tungstenjtita arecharacterized by a laminated or nium, and uranium plate-like crystal structure in--whichthe'metallic atoms are attached to each other in. a single common plane, while thenon-metallic atoms are attached to theme- 7 microns during this interval.

such. surfaces will exhibit .very: strong. resistance to the actionofforces normal to the direction of sheer. Con sequently, these compoundshave excellent lubricating properties and also have excellentz'antieseizing properties. metallic lubricating agents has been selected to denote compounds of this class and this te'rmwillbe used hereinafter.

Electrophoretic deposition: occurs whenv an electrostatic field is established between-two electrodes immersedcwithin: a;:colloidal or gross dispersion of'charged particles, thus causing migrationof the suspended particles toward one ofthe electrodes and producing the deposit of .an adherent coating on that electrode. Exceptional uniformity of coating thickness. and compacting (with an attendant relatively high coating density) are obtainedas compared with dipping, spraying, brushing. and. other conventional methods of application- Irregularly shaped objects can be coated with excellent uniformity and reproducibility of coating. A complete description of the electrophoretic process will be. found in our copending application S.-N. 386,882 filed October 19, 1953.

In another'copending application S.'N. 402,402; filed January 5, 1954, we disclosed a method for electro-' ona base mem ber; the'element soformed comprises a metalmatrix Well bonded to. the basemember and. a-friction modifying agent entrapped. within the interstices of this matrix. The resultingdevice is 'characteriz'eduby a very strong element-member bond and by'long wearing surface prop erties of the element. While. this'method is quite similarto that used in the present application, in contradistinction, the present invention discloses a metal structure provided with a sacrificial layer: and characterized: by a weak layer-structure bond and by a lubricating surfacewhich wears away rapidly.v

The following examples set forth certain well defined instances of the application of this invention. They are, however, not to be considered as limitations thereofi'since many modifications can be made without departing from the spirit and scope of this invention.

Example I A'gross dispersion containing by weight of nickel oxide particles and 25% by weight of molybdenum di sulphide was immersed in ma 5% concentration in above mentioned copending in the dispersion and connected as the anode. Theplate panel separation was adjusted to. 3 inches and a directvoltage of 500 volts was applied between the anode and cathode. Nickel oxide and molybdenum disulphide particles. immediately began to codeposit on one the panel. After a 5 tolO second interval, was-:disconnected and removed. from the bath. deposited coating attained a thickness .of' from The panel, was then fired in the. atmosphere of'hydrogen at a temperature of 1400 seconds.

isopropyl alcohol and diluted surface of the panel" The '00-- F. for a period'of :15: Subsequent. cross-sectional analysis established that the nickel oxide was reduced to nickel in the form. of .amatrix bonded by codiifusion tothesurfaceof the.

The molybdenum disulphide particles did not enter into the reaction as the presence of hydrogen prevented oxidation, but were entrapped within the pores or interstices of the nickel matrix. The ratio by weight of nickel to molybdenum disulphide was found to be approximately 3 to 1.

The nickel-steel bond was found to be sufficiently strong to prevent damage to the coating during normal manual handling; however, the coating could be scratched away by any sharp pointed metal object.

The coated panel was inserted into a metal forming punch and die fixture and a one-half inch diameter section of the panel was drawn to a depth of Va". An uncoated type 304 stainless steel panel of the same dimensions was similarly tested and could not be drawn to a depth greater than Vs" without breaking.

The above process was repeated with different weight percentages of nickel oxide and molybdenum disulphide. When the percentage by weight of the disulphide'was in creased appreciably beyond 30%, the resultant coating did not adhere well to the panel; when this percentage was reduced appreciably below 20% the lubricating propertie were not satisfactory. by holding the percentage by weight of molybdenum disulphide within the range 2229% It was found that the firing temperature within the range 1300-1800" F. was satisfactory.

Example II panel.

A coating 1 to 10 microns thick containing 77% by weight of nickel oxide and 23% by weight of molybdenum telluride was electrophoretically deposited on a segment of molybdenum wire in the same general manner as described above. The coated wire was then fired in a hydrogen atmosphere at a temperature of 1400- 1600 F. for a period of 15 to 25 seconds.

Wire drawing operations were then performed on this coated wire and a like segment of uncoated wire. It was found that the allowable cross-sectional area reduction for a single draw of the coated segment was approximately twice as large as that obtained with the uncoated segment.

The above process was repeated with different weight percentages and with diiferent firing temperatures-and the results were substantially the same as in Example I.

Example III A coating containing 78% by weight of silver oxide particles and 22% by weight of molybdenum disulphide particles was electrophoretically deposited on a titanium sheet in the manner outlined in Example I.

The coated sheet was then fired in helium at a temperature of from 1200 to 1400 F. for a period of 15 to 25 seconds. Subsequent cross-sectional analysis established that the silver oxide had been decomposed to silver in the form of a matrix bonded by codiffusion to the surface of the sheet. The molybdenum disulphideparticles were entrapped within the pores of the silver matrix. The ratio by weight of silver to molybdenum disulphide was. found to be approximately 3 to 1. The amount of silver oxide used to form the matrix may, however, be between 70 and 80% by weight and the corresponding amount of molybdenum disulphide between 30 and 20% by weight.

A titanium sheet with a sacrificial layer prepared in this maner was subjected to the drawing operation described in Example I. The coated sheet was successfully drawn to a depth of /2". An uncoated titanium sheet was similarly tested and could not be drawn to a depth greater than A" without breaking.

Many other materials can be used instead of those disclosed in the working examples. For example, the reducible or decomposable compounds can be oxides, hydrides or decomposable salts of such metals as copper, tin, zinc, chromium and various combinations of these Best results were obtained oxides as well as the oxides, hydrides and salts of nickel and silver. The metallic structure can be formed for example, from zirconium, beryllium and various alloys of these metals as well as steel, titanium and copper alloys.

Although in the above examples we have indicated certain definite firing temperatures, duration of reactions, etc., it is to be understood that any or all of these can be varied widely within the scope of our invention, since the particular conditions of operation are governed largely by the specific end structure desired. For example, the firing temperature must be high enough to perform the desired reduction of decomposition and low enough to prevent softening or melting of the materials used. The actual temperature will vary depending on the characteristics of these materials.

If necessary, that portion of the sacrificial coating which may adhere to the metal structure after the forming operation can be removed either manually or by chemical means such as pickling in selective agents.

Therefore, it is apparent that many widely different embodiments of this invention can be made without departing from the spirit and scope thereof and we do not intend to be limited except as indicated in the appended claims.

We claim:

1. The method of forming a sacrificial lubricating layer upon a selected surface of a metallic structure, said method comprising the steps of electrophoretically codepositing a mixture of a metallic matrix forming material of the group consisting of silver oxide and nickel oxide and a solid lubricant of the group consisting of the sulfides, disulfides, selenides and tellurides of molybdenum, out of a liquid organic medium upon said surface, the amounts of said matrix forming material and solid lubricant producing a layer having 70-80% by weight of metallic matrix and 30-20% of solid lubricant, and heating said structure in a gaseous atmosphere at a temperature to reduce said matrix forming material to form a metallic matrix which is bonded to said surface of said metallic structure, and which entraps and bonds said lubricant to said metallic structure.

2. The method of claim 1 in which the matrix forming material is nickel oxide, the lubricant is molybdenum disulfide, and the structure is heated in a hydrogen atmosphere at a temperature falling within the range 1300- 1800 F. to reduce said nickel oxide to nickel.

3. The method of claim 1 in which the matrix forming material is nickel oxide, the lubricant is molybdenum telluride and the structure is heated in a hydrogen atmosphere at a temperature falling within the range 1400 1600 F. to reduce said nickel oxide to nickel.

4. The method of forming a sacrificial lubricating layer upon a selected surface of a titanium structure, said method comprising the steps of electrophoretically codepositing between 70 and by weight of silver oxide and between 30 and 20% by weight of molybdenum disulphide out of a liquid organic media upon said surface; and heating said structure in an atmosphere of inert gas to a temperature "falling within the range 1200 to 1400 F. for a period sufficient to decompose said silver oxide to silver whereby said layer is formed.

References Cited in the file of this patent UNITED STATES PATENTS 2,202,054 Hensel et al May 28, 1940 2,488,731 Lambert et al. Nov. 22, 1949 2,530,546 Snyder Nov. 21, 1950 2,576,362 Rimbach Nov. 27, 1951 2,640,024 Palmateer May 26, 1953 2,650,975 Dorst Sept. 1, 1953 2,708,726 Atherton May 17, 1955 FOREIGN PATENTS 1,044.212 France June 17, 1953 

1. THE METHOD OF FORMING A SACRIFICAL LUBRICATING LAYER UPON A SELECTED SURFACE OF A METALLIC STRUCTURE, SAID METHOD COMPRISING THE STEPS OF ELECTROPHORETICALLY CODEPOSITING A MIXTURE OF A METALLIC MATRIX FORMING MATERIAL OF THE GROUP CONSISTING OF SILVER OXIDE AND NICKEL OXIDE AND A SOLID LUBRICANT OF THE GROUP CONSISTING OF THE SULFIDES, DISULFIDES, SELENIDES AND TELLURIDES OF MOLYBDENUM, OUT OF A LIQUID ORGANIC MEDIUM UPON SAID SURFACE, THE AMOUNTS OF SAID MATRIX AND SOLID LUBRICANT PRODUCING A LAYER HAVING 70-80% BY WEIGHT OF METALLIC MATRIX AND 30-20% OF SOLID LUBRICANT, AND HEATING SAID STRUCTURE IN A GASEOUS ATMOSPHERE AT A TEMPERATURE TO REDUCE SAID MATRIX FORMING MATERIAL TO FORM A METALLIC MATRIX WHICH IS BONDED TO SAID SURFACE OF SAID METALLIC STRUCTURE, AND WHICH ENTRAPS AND BONDS SAID LUBRICANT TO SAID METALLIC STRUCTURE. 